I have a 1997 KX 125. Several years ago I was riding it and the cone shaped area on the right side case just above the water pump housing popped a hole in the case the size of the bearing. This cone shaped area holds the bearing for the exhaust advance. I replaced the side case with a new one and the same thing happened within a short amout of riding. I have not used the bike since. Does anybody have a suggestions why it is doing this. Thanks!

Kenny